time and date.com a web site where you can find information about Time Zone, Calendar with the holidays of the selected country, World Clock and other Travel tools.
You can customize the clock depending upon the city where you live. For example if you want to know information about Chennai, India, then it looks as shown below.
So you can find information about the Time, Weather, Time Zone, DST, and also Sun and Moon settings for that city.
Other important tools that are available are Meeting Planner, Day Night Map, Distance Calculator and also includes the International Dialing codes for major cities.
timedate.com also provides some useful information regarding leap year, like What is a leap year, Which years are leap years and Why are leap years needed.